Photopolymerizable organopolysiloxane compositions containing SiC-bonded acryloxyalkyl or methacryloxyalkyl groups are known in the art. For example European Pat. No. 016,663 to Rhone-Poulenc Industries, describes photopolymerizable organopolysiloxane compositions containing SiC-bonded acryloxyalkyl or methacryloxyalkyl groups which may be used to prepare adhesive-repellent coatings. In contrast to the organopolysiloxanes described in the European patent, the organopolysiloxanes of this invention cross-link much more rapidly in the presence of atmospheric oxygen.
Also, U.S. Pat. No. 4,011,247 to Sato et al, describes organopolysiloxanes containing both SiC-bonded acryloxyalkyl groups and Si-bonded hydrogen atoms in the same molecule. However, the organopolysiloxanes described heretofore have viscosities of less than 100 mPa.s at 25.degree. C., in order that they may be purified by distillation. Moreover, U.S. Pat. No. 4,011,247 does not disclose using the organopolysiloxanes described therein for adhesive-repellent coatings, nor are they likely to be suitable for such use.
Therefore, it is an object of the present invention to provide a novel organopolysiloxane having a viscosity of at least 100 mPa.s at 25.degree. C. and SiC-bonded acryloxyalkyl groups and Si-bonded hydrogen atoms in the same molecule. Another object of the present invention is to provide a process for preparing an organopolysiloxane having SiC-bonded acryloxyalkyl groups and Si-bonded hydrogen atoms in the same molecule. Still another object of the present invention is to provide an organopolysiloxane having a viscosity of at least 100 mPa.s at 25.degree. C. and having SiC-bonded acryloxyalkyl groups and Si-bonded hydrogen atoms in the same molecule which may be used for coating substrates. A further object of the present invention is to provide an organopolysiloxane having a viscosity of at least 100 mPa.s at 25.degree. C. and having SiC-bonded acryloxyalkyl groups and Si-bonded hydrogen atoms in the same molecule, which may be cross-linked by high energy radiation.